The embodiments described herein relate generally to gas turbine engines and, more particularly, to methods and apparatus for sealing within gas turbine engines.
At least some known gas turbine engines include a plurality of rotating turbine blades or buckets that channel high-temperature combustion gases stream through the gas turbine engines. Known buckets are typically coupled to a rotor within the gas turbine engine. Thermal energy within the combustion gases is converted to rotational kinetic energy by the buckets, which transfer rotational energy from the buckets to the rotor. At least some of these known buckets may be subjected to high temperature environments, and cooling of such buckets may extend their useful life. Specifically, to control an operating temperature of the buckets, at least some known gas turbine engines channel cooling air towards the buckets via an air-cooling system. More specifically, in at least some known gas turbine engines, compressor bleed air is channeled into at least one air channel defined within the rotor and subsequently to the buckets via a plurality of channels extending from the rotor air channels. As the cooling air flows through the buckets, the buckets are cooled, and spent cooling air is then discharged from the buckets into the combustion gas stream.
At least some of the known bucket air-cooling systems into a cavity defined between the buckets and the rotor. More specifically, such cavities are at least partially defined by a dovetail slot on the rotor and an underside portion of a circumferential row of buckets. Such cavities are at least partially sealed by surface contact between a bucket dovetail surface and a rotor dovetail surface. At least a portion of such cavities are also sealed by spraying substances that include materials, for example, aluminum, onto the bucket and/or rotor dovetail surfaces. Other designs for sealing the air supply cavities include uniquely-shaped C-seals, end plates, and/or cover plates that span multiple buckets.
Within at least some known cavities, a portion of the cooling air leaks from the cavity via unsealed portions of the bucket and/or rotor dovetail surfaces into rotor-stator purge cavities, that are in communication with the combustion gas stream, prior to the air being channeled into the buckets. Because the cooling air is supplied by the compressor, such leakage may reduce the efficiency of the gas turbine engine and may cause a size of the compressor to be increased. Such size increases typically increase capital and operational costs.